Nitrogen Incorporation in Potassic and Micro- and Meso-Porous Minerals: Potential Biogeochemical Records and Targets for Mars Sampling.

We measured the N concentrations and isotopic compositions of 44 samples of terrestrial potassic and micro- and meso-porous minerals and a small number of whole-rocks to determine the extent to which N is incorporated and stored during weathering and low-temperature hydrothermal alteration in Mars surface/near-surface environments. The selection of these minerals and other materials was partly guided by the study of altered volcanic glass from Antarctica and Iceland, in which the incorporation of N as NH4+ in phyllosilicates is indicated by correlated concentrations of N and the LILEs (i.e., K, Ba, Rb, Cs), with scatter likely related to the presence of exchanged, occluded/trapped, or encapsulated organic/inorganic N occurring within structural cavities (e.g., in zeolites). The phyllosilicates, zeolites, and sulfates analyzed in this study contain between 0 and 99,120 ppm N and have δ15Nair values of -34‰ to +65‰. Most of these minerals, and the few siliceous hydrothermal deposits that were analyzed, have δ15N consistent with the incorporation of biologically processed N during low-temperature hydrothermal or weathering processes. Secondary ion mass spectrometry on altered hyaloclastites demonstrates the residency of N in smectites and zeolites, and silica. We suggest that geological materials known on Earth to incorporate and store N and known to be abundant at, or near, the surface of Mars should be considered targets for upcoming Mars sample return with the intent to identify any signs of ancient or modern life.

Outcomes of extensive hemilaminectomy with durotomy on dogs with presumptive progressive myelomalacia: a retrospective study on 34 cases.

BACKGROUND: Progressive myelomalacia (PMM) is a fatal complication of progressive ascending and descending necrosis of the spinal cord after acute spinal cord injury. A recent study suggested that extensive hemilaminectomy with durotomy (EHLD) at the intramedullary T2-hyperintense region which performed immediately after magnetic resonance imaging (MRI) improved the survival rate in dogs with presumptive PMM. The objective of this retrospective study was to evaluate the effects of EHLD on halting the progression of PMM in dogs presumptively diagnosed with PMM which had the interval between MRI and surgery. RESULTS: Thirty-four dogs with presumptive PMM which had undergone EHLD with the delay following MRI examination (range, 0 to 3 days) were included. The cranial side of EHLD was set depending on the delay time after MRI, MRI findings, neurological examination and intraoperative macroscopic appearance. Two weeks after surgery, the perioperative survival rate was 97% (33/34). During follow-up with a median time period of 82.5 weeks (range, 0-290 weeks), the postoperative survival rate was 91% (31/34). At the end of the follow-up period, 31 out of 34 dogs were alive without severe postoperative complications while the remaining 2 dogs died from causes not directly attributable to the surgery. There was no improvement in the pelvic limb function of all dogs. CONCLUSIONS: EHLD appears to be effective in halting the progression of presumptive PMM and preventing morbidity even in dogs which had the interval between MRI and EHLD. Our algorithm of determining the range of EHLD may enable to set the appropriate ranges of EHLD in the cases which develop signs consistent with PMM after MRI examination.